Parenteral fluids are usually given in aliquots of 500-1,000 cc at room temperature and desirably at a uniform rate of flow, but current means and/or procedures for insuring uniform rate of flow require electrically-powered positive-pressure pumps which are both expensive and cumbersome in use, the latter because patients being infused often must be moved about, to an X-ray room for example, such necessitating disconnection of the pump motor, with the result that flow of the fluid be stopped until another electrical connection is reached. In orther situations, it is desirable that patients be ambulatory, i.e. walking halls, etc., as when receiving heparin, with the result that the patients' walking is restricted to an area limited by the radius provided by the extension cord.
While various attempts have been made previously to devise a more simple and less cumbersome means for uniform flow administration of parenteral fluids (one such being the subject of Bay U.S. Pat. No. 2,542,461 dated Feb. 20, 1951 which uses a fixed siphon and another being the subject of patent to Fernandez U.S. Pat. No. 2,850,211 employing a float which rides on the surface of the fluid in an inverted bottle-type of reservoir, none has proved acceptable in practice, with the result that uniformity of flow is usually attempted by frequent visits of nurses to the administration set to count the number of drops per minute or by the rate of emptying of a small reservoir made a part of the intravenous tubing.